This invention relates generally to kinescopes and particularly to a deflection system for enhancing the horizontal and vertical deflection in such devices.
Kinescopes include an envelope having a neck portion attached to the narrow end of a funnel portion. A screen is hermetically attached to the wide end of the funnel and the envelope is evacuated. An electron gun is housed within the neck and emits electrons which travel as beams through the funnel to strike the screen. A phosphor coating on the screen luminesces in response to the electron impact to produce a visual output. Because the visual output is provided across the entire face of the screen, it is necessary to vertically and horizontally deflect the electron beam so that the entire screen is sequentially scanned. Typically, this deflection is accomplished by the use of a yoke which is arranged around the outside of the neck portion. The yoke contains horizontal and vertical deflection windings which are respectively energized with horizontal and vertical scanning voltages to effect the required scanning of the entire screen.
The relationship between the length of the tube, that is the distance between the electron gun and the screen, and the horizontal and vertical dimensions of the screen is primarly dependent upon the ability to deflect the electron beam away from the center line of the tube. Accordingly, a decrease in the length of the tube necessitates an increase in either the voltage, i.e., power, supplied to the coils of the deflection yoke, or the number of turns in the coils, of a combination of both of these parameters. An increase in the power of the yoke coils is objectionable because of the resulting continuing increase in the expense of operating the kinescope. An increase in the number of turns in the coils is objectionable because of the increase in size, weight and material costs which naturally result. Therefore, a need exists for a deflection enhancement system which reduces the power required to deflect the electron beam. Such a system could also be used to decrease the length of the tube without increasing either the deflection power or the number of turns in the deflection coils. The present invention is directed to that need.